Generate a summary of the test run so far to the log file and/or standard
output. Both running and differential totals are shown. Output is generated
every n seconds (default 30 seconds (property summariser.interval)) on the appropriate time boundary, so that
multiple test runs on the same time will be synchronised.
This is mainly intended for batch (non-GUI) runs
FIXME : Docs below are outdated, need fixing
Note that the SummariserRunningSample start and end times relate to the samples,
not the reporting interval.
Since the first sample in a delta is likely to have started in the previous reporting interval,
this means that the delta interval is likely to be longer than the reporting interval.
Also, the sum of the delta intervals will be larger than the overall elapsed time.
Data is accumulated according to the test element name.